There are many challenges in the topical application of pharmaceutically active agents. One major objective is to achieve percutaneous delivery of the active agent to the site of treatment. The composition should also have desirable cosmetic characteristics. Application should be easy and should not leave a noticeable residue on the surface of the skin. Moreover, the composition should not cause irritation, discomfort, or inconvenience.
Many antifungal and antibacterial agents are used topically to treat epidermal infections. Some antibiotics, such as tetracycline and clindamycin, are also used to treat acne and other skin diseases that are caused, directly or indirectly, by bacteria. One of the side-effects of systemically administered clindamycin is colitis, which can be dangerous and even fatal. Thus, in treating acne, it is desirable to administer clindamycin topically. Cleocin T®, manufactured by Pharmacia-Upjohn, contains clindamycin phosphate, which is inactive in vitro, but is hydrolyzed in vivo to the antibacterially active clindamycin. Cleocin T® is currently available as a gel, a lotion, and a topical solution, and is used for topical treatment of acne vulgaris.
Others have produced topical formulations containing a pharmaceutically active agent that is sparingly soluble to insoluble in water (e.g., benzoyl peroxide) and a second pharmaceutically active agent (e.g., clindamycin). For example, BenzaClin®, manufactured by Dermik Laboratories, and Duac®, manufactured by Stiefel Laboratories, each contain benzoyl peroxide and clindamycin. BenzaClin® and Duac® are currently available as topical gels. Others have described a suspension foam containing benzoyl peroxide and clindamycin, but the foam contains oil and requires a surfactant in addition to a dispersing emulsifier. See, U.S. Patent Publication 2005/0186147.
Lotion, gels and oil-based foams have the disadvantage of extended rub-in and may leave oily residues. The oil can also exacerbate acne. The solution form readily runs off the site of application, and therefore it is difficult to apply controlled amounts using the solution form.
The present subject matter provides a composition having at least one pharmaceutically active compound, which is useful for topical administration as described herein, as a foamable suspension gel that is non-runny, easy to apply, and does not leave a noticeable residue. The present foamable gel composition provides good control of the application of a small amount of product to the desired area.